National Electrical Installation Standards

Standards as High as Your Own

Thursday, May 18, 2017


Charlie, Thanks for your work on this important public service.

When feeder or branch circuit conductors are run in parallel, does the EGC ever have to be larger than the ungrounded conductors?  The folks that wrote the code handbook seem to think so, BUT the last sentence of .122(F) states "Each equipment grounding conductor shall be sized in compliance with 250.122."  That takes you to 250.122(A) first sentence that states"shall not be smaller than shown in Table 250.122".... but that sentence has a commma and we need to keep reading to the end. Immediately following the mandatory use of the column is the statement "but in no case shall they be required to be larger than the circuit conductors supplying the equipment."  It is in the same sentence.

I think "in no case" means just that, in no case will the table drive you to size an equipment grounding conductor larger than the circuit conductors.  Including the case of the parallel conductors.

If you go back to the more clear wording of 250-95 in previous versions of the code ( I went to the 1993), back before the removal of exceptions was made for "clarity and usability" the intent is much more clear.  Exception 2 has the wording that is now permissive language in .122(A) and exception 2 to 250-95 applies to the parallel conductor statement.

Thanks for giving us your take on this issue.

Greg McMurphy



Hey Greg thanks for your question and you are welcome. This is often a point of confusion. The circuit conductors in a parallel arrangement include all the conductors that make up each phase or grounded conductor. The conductors connected in parallel are added together to determine the equivalent size. So if there were two 500 kcmil conductors in parallel for each phase the area of each phase is 1000 kcmil. Equipment grounding conductors in a raceway that is part of a parallel arrangement might need to be larger than the ungrounded conductors in that raceway but will not need to be larger than all of the ungrounded conductors of any given phase - even in the 1993 NEC.

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